Erect Leaf Research Articles

Mapping of quantitative trait loci determining agronomic important characters in hexaploid wheat ( Triticum aestivum L.).

A set of 114 recombinant inbred lines of the 'International Triticeae Mapping Initiative' mapping population was grown during the seasons 1997, 1998, 1999 and 2000 under several environments. Twenty morphological (glume colour, awn colour, waxiness, leaf erectness, peduncle length), agronomical (ear emergence time, flowering time, grain filling time, ear length, plant height, lodging, grain number, thousand-grain-weight, grain weight per ear, grain protein content, winter hardiness) and disease resistance (powdery mildew, yellow rust, leaf rust, fusarium) traits were studied. Not all traits were scored in each experiment. In total 210 QTLs with a LOD threshold of >2.0 (minor QTLs) were detected of which 64 reached a LOD score of >3.0 (major QTLs). Often QTLs were detected in comparable positions in different experiments. Homologous and homoeologous relationships of the detected QTLs, and already described major genes or QTLs determining the same traits in wheat or other Triticeae members, are discussed.

Variation and inheritance of leaf angle, and its association with spot blotch (Bipolaris sorokiniana) severity in wheat (Triticum aestivum)

One thousand four hundred and seven spring wheat germplasm lines belonging to Indian and CIMMYT wheat programs were evaluated for their leaf angle and resistance to spot blotch caused by Bipolaris sorokiniana during three consecutive crop seasons, 1994–95, 1995–96 and 1996–97.Disease severity was recorded at six different growth stages beginning from tillering to late milk stage. Three crosses (M 3109 × Sonalika, HP 1808 × K 9006 and HD 2662 × K 9006) were made between genotypes with erect and drooping leaves. M 3109 was resistant, Sonalika susceptible while the other three lines possessed moderate resistance to spot blotch. Individually threshed F2 plants were used to advance the generations. Leaf angle and spot blotch resistance were recorded in parents, F1, F3, F4and F5 generations. Leaf erectness in F1 generation showed partial dominance. Evaluation of F3, F4 and F5 progenies(120–150) revealed that leaf angle was under the control of few genes that appeared to be close to three. Germplasm lines with erect and semi-erect leaves displayed lower spot blotch severity than those having drooping and semi-drooping leaves. Lines homozygous for erect leaf posture in F3,F4 and F5 generations showed significantly lower mean AUDPC than those with drooping leaves. A positive correlation (0.58) between leaf angle and AUDPC further indicated a positive influence of leaf erectness on severity to spot blotch disease.

Effects of Flag Leaves and Panicles on Light Interception and Canopy Photosynthesis in High-Yielding Rice Cultivars

The effects of flag leaves and panicles on canopy photosynthesis in a leading cultivar (Nipponbare) and two high-yielding rice cultivars (Takanari and Ghugoku 117) bred in Japan were compared. The total dry matter production was in the order of Takanari > Ghugoku 117 > Nipponbare. Canopy photosynthesis was highest in Takanari throughout the growth season, and was higher in Chugoku 117 than in Nipponbare during the ripening period. The photosynthetic rate in the flag leaf was in the order of Nipponbare > Takanari > Chugoku 117. The light extinction coefficient of canopy was higher in Takanari than in the others. At the middle ripening stage, canopy photosynthesis increased 35 and 17% in Nipponbare and Takanari, respectively, by the removal of panicles and decreased 37 and 48%, respectively, by the removal of flag leaves. In Chugoku 117, canopy photosynthesis was hardly influenced by these treatments. Clearly, the panicles intercept more radiation at the upper layer of the canopy in Nipponbare than in Takanari and flag leaves contribute more to canopy photosynthesis in Takanari than in Nipponbare. However, these effects were small in Chugoku 117. In conclusion, Takanari produces more dry matter than the others due to larger, wider, longer and more erect 1st (flag) and 2nd leaves above the panicles, which intercept more radiation. Chugoku 117 had erect panicles which allowed more radiation to penetrate into the deeper layer of the canopy, resulting in a high dry matter production. The lower panicle height relative to leaf layer and erect panicles are important characteristics for higher yield in rice.

Long wave radiation regime in vegetation-parameterisations for climate research

An analytical and mathematical model that describes the long wave radiation regime inside a vegetation canopy was developed. The model assumptions are: leaves are the only vegetation elements and are arranged in horizontally infinite layers: they are evenly spread in the layers; having random azimuthal direction and defined zenithal direction. Leaves absorb all thermal radiation, do not scatter any and emit isotropic radiation. An adaptation of the `View factor' concept describes radiation exchanges between leaves and leaf layers. The model calculated the amount of irradiance incident on a single tilted leaf from a flat surface (like the ground). It was found that for an isothermal and infinite emitting surface, with both sides of the leaf absorbing identically, the leaf's tilt angle does not influence the amount of irradiance impinging on it. Then the amount of radiation exchanged by two leaves in nearby layers and the irradiance reaching the leaf from a nearby leaf layer are evaluated. Next, the `layer attenuation coefficient', and the `emission coefficient of a leaf layer' are calculated. Finally, the plane parallel radiation transfer equation of thermal fluxes radiance in vegetation canopy is presented. It was concluded that for an infinite, homogeneous and isothermal leaf canopy with erect leaves, outside irradiance penetrates into deeper layers and less thermal radiation is released to the surroundings, than for the plane leaf canopy case. From this point of view an erect leaf canopy is better suited to cold climates.

Classifying the geometry of canopies from time variations of red and near-infrared reflectance

A new method is suggested for classifying the geometry of canopies from red and near-infrared reflectance values measured from a nadir view. The method relies on the fact that the slope of a very strong linear statistical relationship ( R 2 > 0.95) between two indices varies significantly with the structure of the canopy. The first index (RVI c) is the ratio between reflectance in the near-infrared (NIR) and in the red channels, where intercept ( b) of the soil line is substracted from the NIR: RVI c = (NIR - b) / Red. The second index (GEO) in a new index calculated from the indices (PVI and SLI) introduced by Richardson and Wiegand (1977; Wiegand and Richardson, 1982): GEO = (SLI 2 + PVI 2) / (SLI − PVI). GEO is much more sensitive to canopy architecture than is RVI c. Thus the ratio of RVI c vs GEO, or the slope in such graphs, increases as leaf angle increases. Applied to three wheat cultivars, the smallest slope of the RVI c vs. GEO is for the cultivar that differed from the others by a mean leaf angle of about 15° or less. The significance of the approach is that it helps identify leaf angle differences among observed canopies when leaf area index (LAI) is unknown but has a sufficient space variability. This method is illustrated by the RVI c-GEO relations within a durum wheat field in the south of France observed on two SPOT satellite scenes. An increase of leaf erectness between tillering stage and early grain filling phase (2 weeks after anthesis) is clearly shown by the evolution of the slope of the RVI c vs. GEO relation.

STABILITY IN YIELD PERFORMANCE OF ERECT LEAF GENOTYPES OF FINGERMILLET

Stability parameters for grain yield were worked out for five erect leaf genotypes of fingermillett (ragi) viz., IE 252, IE 503, IE 629, IE 798 and TNAU 5 and four normal high yielding varieteies, PR 202, Co.7, Co.13 and Paiyur 1. Significant differences were observed for genotype. environment and genotypes x environment interaction. TNAU 5 and PR 202 recorded above average response for grain yield, low regression coefficient and low mean square deviation from regression indicating their adaptability to unfavourable environments. All other varieties except IE 252 were found to be adaptable for favourable environment. In general, mean square deviation from regression was very low in all the genotypes studied. There was a decline in grain yield of these genotypes when planted at higher plant density levels.

Comparison of a common, rare and declining plant species in the Asteraceae: possible causes of rarity

Three forbs of contrasting abundance were compared with the aim of identifying ecological traits that may be associated with differences in abundance in Australia. Hypochoeris radicata (an extremely common, exotic species), Cymbonotus lawsonianus (rare in some regions, moderately common in others) and Microseris lanceolata (once widespread but which has dramatically declined) are all species of grasslands and grassy woodlands. Habitat details and phenological observations are reported from the New England Tablelands, New South Wales where the three species co-occur. This information is synthesized with that available in the literature. Part of the success of H. radicata relates to its broad environmental tolerance. Although C. lawsonianus and M. lanceolata are both widely distributed in Australia, the range of habitats in which they occur is more limited. The depletion of M. lanceolata populations is largely attributed to a vulnerability to domestic grazing animals that may be linked to its palatability and architecture. The more common C. lawsonianus and H. radicata appear more tolerant of grazing and mowing and may be advantaged by their ability to form flat rosettes. Despite its occurrence at sites with soil disturbance, C. lawsonianus is still rare in comparison with H. radicata. It may be restricted by a lack of phenotypic plasticity that prevents plants adopting an erect leaf position under more competitive situations. A number of rare native herbs appear to be disturbance-dependent, and it is suggested that C. lawsonianus may share with them highly specific ecological requirements that make both undisturbed and human-disturbed sites sub-optimal for their persistence.

Leaf Posture, Grain Yield, Growth, Leaf Structure, and Carbon Isotope Discrimination in Wheat

The purpose of this study was to examine how differences in leaf angle may affect grain yield of wheat by changes in the relative contribution of yield components or changes in the pattern of crop growth. Leaf structural changes and their influence on plant water status and carbon isotope discrimination were also studied. A collection of pairs of bread wheat (Triticum aestivum L.) lines (PL) differing in leaf angle were grown under irrigation during two consecutive years at Sonora, Mexico. Erect leaf lines did not have higher yields than droopy leaf lines, but erect lines did have 5 to 16% greater number of kernels per unit of ground area. Droopy lines had a lower number of spikes per unit ground area, a greater number of kernels per spike, and a greater weigh of mature kernels than droopy lines. Therefore, the lack of differences in yield apparently was associated with yield component compensation. Differences between PL in discrimination against 13C (∆) in mature kernels, relative water content of flag leaves, canopy temperature, leaf area, and degree of leaf tip burning suggested higher transpiration rates (and thus lower water use efficiency) in the erect lines. For example, ∆ in kernels was consistently higher in the erect lines than in the droopy lines. In addition there was a significant (r = −0.85, P < 0.05) negative correlation between canopy temperature during grain filling and ∆. Grain yield was positively correlated (r = 0.50, P < 0.05) with ∆ of kernels. Although wheat genotypes with erect leaves did not show conclusive superiority, nevertheless selection for a more erect growth habit may result in increased yield. However, the possible existence of allometric relationships among leaf erectness and smaller leaves, spikes, and stems make progress in increasing yield a complex task.

New Series and Species of Lepanthes (Orchidaceae) from Ecuador

Three new series in Lepanthes sect. Lepanthes are described, and sixteen new species of Lepanthes are described from Ecuador. Prior to 1983, 30 species of Lepanthes Swartz had been attributed to Ecuador, mostly by Lindley, Reichenbach, and Schlechter from collections mostly by Jameson and Sodiro. Other better known collectors never bothered to collect a Lepanthes. Today, 295 species are known from Ecuador, but many of these have not yet been published. In order to handle this large number of basically similar species, series based on key-characters are employed. Some individuals of a few species fall between series. Therefore, a few species may be listed in more than one series. The following 16 previously undescribed species are all members of section Lepanthes. Fourteen are in Lepanthes subsect. Elongatae (Luer, 1987) and two are in Lepanthes subsect. Lepanthes. Four series, two in each subsection, are recognized. Lepanthes subsect. Lepanthes ser. Lepanthes is characterized by a congested inflorescence that remains shorter than the leaf. It contains by far the greatest number of species in the genus. Lepanthes subsect. Lepanthes ser. Filamentosae is characterized by a densely flowered inflorescence that is borne beyond the leaf by an elongated peduncle. Lepanthes subsect. Elongatae ser. Elongatae is characterized by a lax or (distantly flowered) inflorescence that is longer, or becomes longer than the leaf. Lepanthes subsect. Elongatae ser. Breves is characterized by a loose inflorescence that remains shorter than the leaf. In the Pleurothallidinae a distantly flowered inflorescence is characterized by the exposed portion of the rachis between floral bracts being longer than the pedicels. Lepanthes ser. Lepanthes. TYPE: Epidendrum ovale Swartz, Prodr. 125, 1788 = Lepanthes ovalis (Swartz) Fawcett & Rendle. Lepanthes ser. Filamentosae Luer, series nov. TYPE: Lepanthes filamentosa Luer & Hirtz, Novon 3: ???, 1993. Racemus congestus quam folio longiore. NOVON 3: 442-454. 1993. Lepanthes ser. Elongatae Luer, series nov. TYPE: Lepanthes elongata Luer & Hirtz, Lindleyana 2: 99, 1987. Racemus laxus quam folio longiore. Lepanthes ser. Breves Luer, series nov. TYPE: Lepanthes monoptera Lindley, J. Bot. 1: 10, 1834. Racemus laxus quam folio breviore. The vast majority of the species of Lepanthes from Ecuador that have come to my attention since 1978 have been discovered by Alexander C. Hirtz, a mining engineer in Quito, Ecuador. Not only does he have the enthusiasm to hunt them and an uncanny ability to find them, but he knows them by name, habitat, and locality, far better than I. He has also had the perseverance to photograph nearly every one. For these reasons I do not consider him merely the collector. I am pleased to include his name with mine in the following new descriptions. Lepanthes andreettae Luer, sp. nov. TYPE: Ecuador. Morona-Santiago: without locality, collected by A. Andreetta, probably in the vicinity E of Paute, ca. 1,800 m, flowered in cultivation at Paute by A. Andreetta, C. Luer 13855 (holotype, MO). Figure 1. Planta parva; inflorescentia racemosa laxa folio elliptico multilongiore; floris sepalis purpureis late luteomarginatis, sepalo dorsali synsepaloque anguste ovatis acuminatis, synsepalo supra medium inciso, petalis transverse bilobis, lobis triangularibus, superiore ter majore, labelli laminis duabus anguste ovatis acuminatis, corpore angusto, appendice digitiformi pubescenti. Plant small, epiphytic, caespitose; roots slender. Ramicauls slender, erect, 5-8 mm long, enclosed by 2-3 loose, microscopically ciliate, lepanthiform sheaths. Leaf erect, coriaceous, elliptical, obtuse, 12-16 mm long, 6-8 mm wide, the base cuneate into a petiole 2-3 mm long. Inflorescence a loose, distichous, successively several-to many-flowered raceme up to 9 cm long, borne by a slender peduncle 15-20 mm long; floral bract 2 mm long; pedicel 1.5-2 mm long; ovary 1 mm long; sepals purple This content downloaded from 157.55.39.30 on Thu, 26 May 2016 04:34:09 UTC All use subject to http://about.jstor.org/terms Volume 3, Number 4 1993 Luer Lepanthes from Ecuador

Use of Photosynthetically Active Radiation by Sunflower and Sorghum

Intercepted, reflected, and transmitted photosynthetically active radiation (PAR) of sunflower (Helianthus annuus L., cv. Hysun 354) with predominantly horizontal leaf orientation and sorghum (Sorghum bicolor (L.) Moench, cv. Funk's G522DR) with predominatly erect leaf orientation, two important dryland crops, were measured to contrast their light use. In addition, the extinction coefficient (k), light-use efficiency (LUE), and the relationship between evapotranspiration (ET) and PAR were compared. Sunflower intercepted more PAR than sorghum. It also reflected less and transmitted less PAR than sorghum. Maximum interception of PAR was 98 per cent for sunflower and 95 per cent for sorghum. Maximum interception occurred at an LAI of 3.14 in sunflower and 3.55 in sorghum. The k value of sunflower (0.83) was higher than that of sorghum (0.62). The LUE value of sorghum (2.8 g m-2 per MJ m-2) was higher than that of sunflower (2.3 g m-2 per MJ per m-2). Sunflower had a higher ET than sorghum, for the same amount of PAR intercepted. It lost 0.80 mm of water per MJ m-2 of intercepted PAR compared to 0.69 mm water per MJ m-2 for sorghum. The results suggested that, because sunflower had a higher ET per unit intercepted PAR, the ET of sunflower had a higher proportion of transpiration than did the ET of sorghum.

Three New Species of Masdevallia (Orchidaceae) from South America

The following three species described as new in Masdevallia represent three sections of subgenus Masdevallia. Masdevallia goliath is a successively flowered, round-stemmed species of section Coriaceae subsection Durae. Masdevallia mascarata is a member of section Polyanthes subsection Alaticaules, distinguished by triquetrous peduncles. Masdevallia ricii is a member of subsection Saltatrices, noted for the long sepaline tubes, of section Masdevallia. Masdevallia goliath Luer & Andreetta, sp. nov. TYPE: Ecuador. Prov. of Morona-Santiago: epiphytic, near Bomboiza, alt. 1,700 m, collected by A. Andreetta, flowered in cultivation at Paute, 24 May 1988, C. Luer 13629 (holotype, MO). Figure 1. Species haec Masdevalliae ayabacanae Luer affinis, sed sepalorum caudis longioribus illis lateralium approximatis, petalis minute asperatis et labelli marginibis apicalibus valde revolutis differt. Plant medium to large, epiphytic, caespitose; roots coarse. Ramicauls stout, erect, 2-3 cm long, enclosed by 2-3 tubular sheaths. Leaf erect, thickly coriaceous, narrowly obovate, obtuse, 10-23 cm long, 2.5-3.5 cm wide, gradually narrowed below into an indistinctly petiolate base. Inflorescence a congested, successively few-flowered raceme borne by a terete, purplish, ? horizontal to ascending or descending peduncle 20-35 cm long, with 2-3 close bracts below the middle, from low on the ramicaul; floral bract tubular, 15 mm long; pedicel 10-15 mm long; ovary 10 mm long; sepals fleshy, dark red-purple, glabrous externally, minutely glandularpubescent within, the dorsal sepal narrowly triangular-ovate, 20-30 mm long, 12-15 mm wide, the acute apex attenuated into a slender, erect, orange to green tail 6-9 cm long, connate to the lateral sepals for 6-9 mm to form a short, conical tube, the lateral sepals ovate, oblique, ca. 35 mm long, + prominently veined within, connate 17-23 mm into a concave lamina, 26-34 mm wide, the acute apices approximate and attenuated into tails 5-9 cm long; petals cartilaginous, yellow, dotted with purple, minutely asperate-verrucose, broadly oblong, shortly unguiculate, 5.5 mm long, 3.25 mm NOVON 2: 6-11. 1992. wide, the truncate apex bilobed with a thick, obtuse apiculum in the sinus, both halves callous, shallowly sulcate centrally; lip yellow-orange, dotted with redpurple, thick, oblong-ligulate, 6 mm long, 2.75 mm wide, the apical third thickened, verrucose, with revolute margins, the apex rounded with a thick, verrucose callosity beneath, the disc shallowly sulcate, the base subcordate, hinged beneath; column cream-colored, stout, semiterete, 4 mm long, the foot thick with a very short, incurved extension. Other specimens examined. PERU. AMAZONAS: near Tarapoto, collected by M. Arias, flowered in cultivation by W. Rhodehamel at Hoosier Orchid Co., Indianapolis, Indiana, W. Rhodehamel s.n. (MO). Etymology. Named for the Philistine giant Goliath. This large, robust species occurs locally in cloud forests of southeastern Ecuador and northeastern Peru. It is closely allied to the Peruvian Masdevallia ayabacana from the mountains of northwestern Peru, but M. goliath is distinguished by the flowers with longer sepaline tails. The apices of the lateral sepals are approximate so that the bases of the tails touch in the natural position. The angle between the apices of the lateral sepals of M. ayabacana is obtuse. The cartilaginous petals are minutely exasperate on the margins and nearby. The petals of M. ayabacana are smooth. The margins of the verrucose apical third of the lip are acutely revolute resting against a prominent tuberosity beneath the apex. Masdevallia mascarata Luer & Vasquez, sp. nov. TYPE: Bolivia. Santa Cruz: epiphytic in moist forest south of Yapacani, alt. 650 m, 7 Sep. 1991, C. Luer, J. Luer, L. Moreno & D. Ric 15402 (holotype, MO; isotypes, AMES, LPB). Figure 2. Species haec Masdevalliae auropurpureae Reichb. f. affinis, sed pedunculo ascendenti vel horizontali, synsepalo ovato et labello lateriore differt, etiam M. zahlbruckneri Krzl. persimilis, sed pedunculo triquetro, petalis oblongis et labello plicato differt. Plant small to medium in size, epiphytic, caespitose; roots slender. Ramicauls slender, erect, 0.51.5 mm long, enclosed by 2-3 thin, tubular sheaths. This content downloaded from 157.55.39.176 on Sat, 09 Apr 2016 06:52:52 UTC All use subject to http://about.jstor.org/terms Volume 2, Number 1 1992 Luer 7 South American Masdevallia r? i, I '.? r '??l?L1! r? C !..?? E?,? r L ??

The yield of durum wheats released in Mexico between 1960 and 1984

SummaryTwo trials designed to measure progress in the yield of durum wheat cultivars released in Mexico by the Institute Nacional de Investigaciones Agrícolas over the period 1960–84 were grown in the Yaqui Valley, Sonora, Mexico, during the 1983–4 and 1984–5 cropping seasons. The trials compared grain yield, above-ground biomass, harvest index (ratio of dry grain yield to dry above-ground biomass), yield components, grain-growth rates and phenological characters for eight key cultivars and the modern advanced line, Carcomun ‘S’, when grown at a high level of agronomic inputs and management.The grain yield of durum wheat was estimated to have risen for 25 years of breeding from 3·70 to 8·40 t/ha. The estimated average annual rates of increase in grain yield for the periods 1960–71 and 1971–85 were 251 and 121 kg/ha respectively. Grain yield improvements were based on a linear increase in the number of grains/m2 over the 25-year period, the result of more grains per spikelet. An improved above-ground biomass at maturity was a feature of the two modern genotypes, Altar 84 and Carcomun ‘S’. Harvest index increased with each new cultivar up to the release of Mexicali 75 in 1975, but thereafter the higher grain yields achieved with the modern genotypes were not associated with a higher harvest index. Thousand-grain weight remained steady for the released cultivars but fell slightly for the advanced line Carcomun ‘S’. Improvements in yield were not associated with a longer cropping cycle.It is concluded that a breeding strategy combining selection for morphological characters thought to confer high yield potential, such as a more erect leaf posture and high number of grains per spikelet, with selection for grain yield per se has been successful in improving the grain yield of durum wheats adapted to north-west Mexico. Improvements have come not only in the size of the grain sink and the efficiency of assimilate partition to grain but also in the biomass produced above ground.

Effect of Erect Leaf Angle on Grain Yield in Barley1

Breeding for erect leaf angle has been suggested as a method for increasing grain yield in cereal crops. This study was designed to investigate the effect of erect leaf angle on grain yield in barley (Hordeum vulgare L.). Five cycles of crossing and selection were used to incorporate the erect leaf of C16146 into adapted Minnesota barleys. Subsequently, erect leaf lines from five populations were evaluated in yield trials. In addition, the yield response of erect leaf lines was compared to check cultivars at planting rates of 56, 94, and 132 kg ha−1. No significant difference was found for grain yield between erect leaf lines and check cultivars in three populations. Comparisons of erect and horizontal leaf progeny in two other populations showed no difference in one population; however, the horizontal leaf group was higher yielding in the second. The yield responses of erect and horizontal leaf‐types to the three planting rates were similar, although significant interaction was observed for kernel number and weight, suggesting that canopy type may influence these components. Erect leaf lines had less culm flex, more erect spikes, lower head number, later maturity, and greater lodging resistance than horizontal leaf lines. These associations with the erect leaf trait, which likely resulted from pleiotropy, were confounded with the effect of erect leaves and likely reduced the chances of finding a positive grain yield response. Although the potential of increased lodging resistance and the leaf‐type density interaction for kernel number and weight offer some encouragement for continuing research, results from our study provide little or no evidence that erect leaf angle enhances grain yield in barley.

Screening a Wheat Collection for Leaf Position at Different Stages of Growth

AbstractA collection of hexaploid ‐wheat consisting of 1400 entries from 36 countries was screened for leaf position at four stages of growth over two years. At the shooting stage, more than 80 % of the entries showed the curved position of the flag and the second leaf, about 15 % the erect position, while the horizontal position did not occur. At the heading stage more than 10 % of the genotypes with curved and some with erect position assumed horizontal position. At the milk stage, half of the genotypes with the erect position in earlier stages of growth assumed horizontal and even pendulous position; the majority of genotypes had curved position of leaves. At the dough stage, only about 2 % of the genotypes maintained erect flag leaf position, while 45 % had curved and about 45 % pendulous position of leaves.When an erect leaf assumes horizontal position, the lamina is completely straight without any curving, which is different from genotypes classified as having horizontal position at heading and milk stage. The position of the second leaf, in general, followed the pattern of the flag leaf. Through the stages of growth the curved position was more stable than either erect or horizontal positions. Leaves were more erect and stable in position under conditions with lower rainfall and higher temperatures (1983) than in the rainy year with lower temperatures (1984). Most of the high‐yielding cultivars with short straw had a curved position, which is probably the consequence of unintended selection to fit a dense canopy.

Screening of Barley Varieties for Drought Resistance

AbstractBarley varieties were screened for their efficient drought enduring ability and associated characters which may be useful in breeding programmes. The characters studied were: relative water content, content of proline, chlorophyll stability index (CSI), and percentage grain loss per plant due to water stress subjected to 10 days from jointing to boot stage. Proline and chlorophyll stability index were greatly associated with drought response (r =+0.54; ‐0.49), flag leaf area (r =+0.69; ‐0.51) and, to a certain extent, with leaf number (r = ‐0.35 and +0.34). Among the studied 19 varieties of barley, only three (DL 192, DL 36, DL 3) showed high enduring ability, of these the former two fall in the early, and the last one in the late flowering group. Morphological architecture of DL 192 had gathering type tiller (narrow tiller angle), wider and floppy leaves and it also bears physiological characters (high proline and high relative water content, and low value of chlorophyll stability index) necessary for drought resistance. DL 3 and DL 36 had dispersing type tiller (wider tiller angle) and erect leaf with good leaf area/plant, but unit leaf area was low in DL 3 (relates with shading behaviour reducing water loss). Other relations of drought resistance are briefly discussed in the text. An appraisal of the various traits revealed that high proline content, and low CSI (biochemical characters), earliness, larger flag leaf area and fewer leaves per plant (morphological characters) were directly correlated with productivity of the cultivars under drought conditions. These characters could be used as a guideline for breeding drought resistant cultivars of barley.

Untersuchungen zur Ertragsbildung kurz‐ und langstrohiger Winterweizensorten

Abstract Investigations about the yield formation of Winter Wheat Cultivars with Short and Long Straw. The yield formation of winter wheat cvs with semi‐dwarf, short straw and long straw growth habit was investigated over three years in field and glasshouse trials.The cv with semi‐dwarf growth habit had less earbearing tillers and spikelets per ear, an essential lower reduction rate of spikelets and more kernels per spikelet. This cv ranged medium in thousand kernel weight (tkw). Cvs with short straw differed from cvs with long straw through a lower reduction rate of tillers and a lower tkw.No differences were found in the time of development of generative organs in specific growth phases. Cvs with short straw had advantages in assimilation by means of higher leaf area indices from tiller formation till anthesis and a better light penetration in the canopy due to a more erect leaf orientation. These characters may have been decisive for the higher survival of tillers. The cvs with a long straw however had a higher tkw, properly due to a less compact ear and a higher assimilate gain during kernel filling. Only small differences were found in root growth in favour of the cvs with short straw. The semi‐dwarf cv had the shortest roots. The cv “Kanzler” with a long straw had the best drought resistance.

Cultivation and breeding of Digitalis lanata in the Netherlands.

After the second world war Marshall Aid funds were used to establish a cooperative organisation for growing, drying, and selling Digitalis lanata (and other medicinal, aromatic, and culinary herbs) in the Netherlands. The crop is sown in mid April and the fully mechanised harvest of the leaves takes place from September to late November. The leaves are dried for 10-12 hours at 50 degrees C maximum. The aim of breeding trials is to improve leaf production, erect leaf attitude, resistance to Septoria leaf spot and to bolting, and a higher dry matter and digoxin content.

A mechanistic simulation analysis of water use, leaf angles, and grazing in East African graminoids

A simulation model was constructed in order to interrelate the effects of defoliation by large mammalian herbivores with growth, photosynthesis, water use and light interception of representative graminoid vegetation from East Africa. Abiotic submodels describing water flows, light penetration and interception, and energy balance relationships were interfaced with a graminoid growth model that was specifically designed to examine grazing responses. Defoliation reduced rainfall interception and reduced transpiration, thereby increasing soil and plant water levels. Morphological adaptations made compensatory shoot growth possible, but grazing effects on plant water contents largely determined the degree of compensatory growth. Aboveground productivities were greatest at moderate grazing intensities while belowground productivities were greatest at lower grazing intensities. The success of a given water use strategy depended on simultaneous consideration of the abiotic environment and grazing. Under frequent grazing soil water conservation and reduced shoot/root ratio counteracted the depletion effect of high stomatal conductance on plant water content. Consequently photosynthesis under frequent grazing was maximized by higher stomatal conductance. Canopy geometry was adaptive for maximal light harvesting subject to the constraints imposed by transpiration, water availability, and herbivory. Total photosynthesis was increased greatly by erect leaf angles for all but not short grasses. For frequently grazed short-grasses the benefits of prostrate leaves associated with escape from grazing exceeded the associated costs of reduced photosynthate.

Effects of dense planting and artificial shading on five maize hybrids

The effect of light stress originating from artificial partial shading and from selfshading caused by dense planting on the grain yield of five maize communities differing genotypically in earliness was studied. The sensitivity of plants in different growth stages to light stress was also investigated. Finally, the possibility of relieving the light stress by manipulating leaf inclination was tested in dense populations. Increasing the density of a 5 plants/m 2 community by two and a half times seemed as detrimental for grain yield per plant as decreasing the community's illumination by half by shading. The relative performance of hybrids was changed both by artificial shading and by self-shading. No relationship was found between earliness and response to light stress nor between the response to artificial shading and the response to self-shading resulting from dense planting. Both pot and field trials showed higher sensitivity of plants to light stress during the period 10–20 days after silking than during earlier periods. Leaf erectness caused a small grain yield increase in the 10 plants/m 2 density when soil conditions were optimum. Under soil moisture stress it had no effect in the 10 plants/m 2 density while it depressed yield at higher densities.

Genetic Variation for Canopy Architecture and its Use in Wheat Breeding1

Genetic studies showed that two genes control the dense spike (short rachis internodes) of PI 190982 (Triticum aestivum L., sphaerococcum group), a tall wheat cultivar from Spain that has erect and short leaves. Few genes, most likely two or three, controlled most observed differences in flag leaf angle and length. Selection allowed the isolation of erect‐leaved types that yielded about 45% more grain than PI 190982 but about 20% less grain than standard cultivars. Erect and nonerect derived lines did not differ in yields between row spacings of 15 and 30 cm in field experiments in 2 years. PI 190982 appears to be a useful germplasm source for modifying canopy architecture, but the role of leaf erectness in reaching new high yield levels requires additional study.